Aim The contemporary coexistence theory suggests that species pool, environmental filtering, dispersal assembly processes, ecological drift and biotic interactions collectively determine the β‐diversity of communities. However, we know little about the biogeographical patterns of the β‐diversity of microbial communities harbouring the alkaline phosphatase phoD gene (phoD communities, hereafter) and whether these mechanisms are all‐important in shaping phoD communities’ β‐diversity in natural steppe ecosystems. Location Northern Hemisphere steppes. Time period July to August 2018. Major taxa studied Alkaline phosphatase (phoD gene) encoding community. Methods Using the high throughput amplicon sequencing method, soil phoD communities were comparatively studied along three representative regions of the Northern Hemisphere steppes, namely the Qinghai‐Tibetan Plateau, Inner Mongolian Plateau and the Loess Plateau. Each region harbours three types of steppes (habitats): meadow, typical and desert steppes. Results We observed significantly higher phoD β‐diversity in the Qinghai‐Tibetan than in the Loess and Inner Mongolian Plateaus and significantly lower β‐diversity in the typical steppes than in other steppe types. The decay rates of phoD β‐diversity with geographical distance varied in different steppe regions and types. The phoD β‐diversity was not significantly influenced by species pool; instead, environmental filtering, dispersal assembly processes, ecological drift and biotic interactions jointly shaped the β‐diversity patterns. The β‐deviation variations (β‐diversity excluding the effects of species pool) were influenced by spatial and environmental factors and biotic interactions, among which soil pH was the key environmental determinant. The soil pH driving β‐diversity mechanism was steppe region and habitat specific. Main conclusions The biogeographical patterns of phoD β‐diversity were mainly driven by local community assembly processes in the Northern Hemisphere steppes.

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Background Root-associated microbiomes are important for plant nutrient uptake, disease suppression and plant growth. It is important to reveal wheat-root associated microbial community assembly and dominant drivers determining their variability. Methods Using 16S rRNA gene profiling, we investigated the effects of sample type, location, growth stage and variety on prokaryotic communities in the root endosphere and rhizosphere of wheat and bulk soil based on the field samples including 5 varieties from 4 locations along similar latitude with the distance about 157 to 800 km apart between any two locations.Results Prokaryotic communities were more diverse in the bulk soil and rhizosphere than in root endosphere. Wheat-root associated prokaryotic community assembly was shaped predominantly by sample type, while within each sample type, location had stronger effects on the variation in prokaryotic community than growth stage or variety. Wheat variety effects varied substantially among different locations and growth stages in root endosphere and rhizosphere samples, and the variety effects were location-specific and growth stage-specific. Root endosphere specially enriched Pseudomonas, relative to other two sample types, while rhizosphere mainly enriched Bacillus. Conclusions This study characterized prokaryotic communities of wheat-root endosphere and rhizosphere and their relationships, and demonstrated significant interactive effects between wheat variety, location and growth stage on prokaryotic community assembly in field condition.

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